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<!DOCTYPE concept

  PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">

<concept id="GUID-1AA392CB-F638-5D35-993E-4A26D67A7C98-GENID-1-12-1-26-1-1-11-1-1-3-1-4-1-5-1" xml:lang="en"><title>How

to retrieve characteristics</title><prolog><metadata><keywords/></metadata></prolog><conbody>

<p>The following example demonstrates the use of the legacy selector to retrieve

the characteristics of an asymmetric cipher object. In the example, an implementation

object is constructed (making use of an RSA Key Pair also generated by the

framework) and returned. The plug-in characteristics and extended characteristics

associated with the object are then accessed. </p>

<codeblock id="GUID-CF2DF77C-90BD-56A0-A27D-89C4DA18EDCD-GENID-1-12-1-26-1-1-11-1-1-3-1-4-1-5-1-2-2" xml:space="preserve">#include &lt;cryptoasymmetriccipherapi.h&gt;

#include <cryptokeypairgeneratorapi.h>

#include <cryptospidef.h>

#include <plugincharacteristics.h>

#include <extendedcharacteristics.h>

#include <keypair.h>

// Constant definition for the RSA key pair generator exponent value

const TInt KKeyExponent = 65537;

using namespace CryptoSpi;

// Create a new CCryptoParams instance to contain the RSA Key Pair initialization data

CCryptoParams* keyParams = CCryptoParams::NewLC(); 

// Create an RSA Key Pair and Key Pair Generator object pointers

CKeyPair* keyPair = NULL;

CKeyPairGenerator * keypairImpl = NULL;                

// Set the RSA Key Pair Generator initialization parameters reate an RSA key pair

keyParams->AddL(KKeyExponent, KRsaKeyParameterEUid);

keyParams->AddL(KRsaPrivateKeyStandard, KRsaKeyTypeUid);

// Retrieve an instance of an RSA Key Pair Generator implementation from the framework

CKeyPairGeneratorFactory::CreateKeyPairGeneratorL( keypairImpl,

                                                   KRSAKeyPairGeneratorUid,

                                                   keyParams);

CleanupStack::PushL(keypairImpl);

// Create an RSA Key Pair    

keypairImpl->GenerateKeyPairL(1024, *keyParams, keyPair);

CleanupStack::PushL(keyPair);

// Create and initialize a pointer for the asymmetric cipher implementation object        

CAsymmetricCipher* asymmetricCipherImpl = NULL;

// If successful, the 'CreateAsymmetricCipherL' method returns KErrNone and sets the 

// asymmetricCipherImpl pointer to point to the constructed implementation

TRAPD(err, CAsymmetricCipherFactory::CreateAsymmetricCipherL(asymmetricCipherImpl,

                                                             KRsaCipherUid,

                                                             keyPair->PrivateKey(),

                                                             KCryptoModeEncryptUid,

                                                             KPaddingModeNoneUid,

                                                             NULL));

// Having successfully constructed the asymmetric cipher implementation object, 

// it is possible to retrieve the plug-in characteristics associated with it

if (asymmetricCipherImpl && (err == KErrNone))

 {

 CleanupStack::PushL(asymmetricCipherImpl);

 // Retrieving common and algorithm-specific characteristics

 // Create a constant pointer of type TCharacteristics used to access the

 // asymmetric cipher plug-in's common and algorithm-specific characteristics

    const TCharacteristics* chars(NULL);

 // Retrieve the common and algorithm-specific characteristics by calling the

 // 'GetCharacteristicsL' method passing in TCharacteristics pointer

 asymmetricCipherImpl->GetCharacteristicsL(chars);

 // Static cast the characteristics to type TAsymmetricCipherCharacteristics

 const TAsymmetricCipherCharacteristics* asymmetricChars = 

  static_cast<const TAsymmetricCipherCharacteristics*>(chars);

 // Retrieve the common characteristics from the TASymmetricCipherCharacteristics

 // object

 const TCommonCharacteristics* asymmetricCommonChars = &asymmetricChars->cmn;

    TUid implementationId;

    TBool hardwareSupported;

    TRomLitC16 creatorName;

    TInt maximumKeyLength;

    TInt32 supportedPaddingModes;

 // Example of extracting asymmetric common characteristics

 implementationId.iUid = asymmetricCommonChars->iImplementationUID;

 hardwareSupported = asymmetricCommonChars->iIsHardwareSupported;

 creatorName = *(asymmetricCommonChars->iCreatorName);

 // Example of extracting asymmetric algorithm specific characteristics

 maximumKeyLength = asymmetricChars->iMaximumKeyLength;

 supportedPaddingModes = *(asymmetricChars->iSupportedPaddingModes);

 //Retrieving extended characteristics

 // Create a constant pointer of type CExtendedCharacteristics used to store and

 // access the asymmetric cipher plug-in extended characteristics. Retrieve

 // the data by calling the 'GetExtendedCharacteristicsL' method and store the

 // returned pointer

 const CExtendedCharacteristics* extendedChars =

  asymmetricCipherImpl->GetExtendedCharacteristicsL();

 // Const casting the pointer to the CExtendedCharacteristics object allows it to

 // be pushed onto the cleanup stack

 CExtendedCharacteristics* ncExtendedChars =

  const_cast<CExtendedCharacteristics*>(extendedChars);

 CleanupStack::PushL(ncExtendedChars);

 TInt concurrency;

 // Each of the extended characteristics for the particular cryptographic

 // implementation can then be accessed by passing the UID value into the

 // appropriate 'Get' method

 concurrency = extendedChars->GetTIntCharacteristicL(KConcurrencyTypeUid);

 // Alternatively, extended characteristic retrieval can be achieved via the

 // ListExtendedCharacteristics() method of the CExtendedCharacteristics Object.

 // Using the 'ListExtendedCharacteristics' function returns a pointer to a

 // CCryptoParams object, that contains a list of all associated extended

 // characteristics

 const CCryptoParams* extendedCryptoParams = 

  extendedChars->ListExtendedCharacteristics();

 TBool exclusiveUse;

 // The extended characteristics can then be accessed in much the same way as 

 // before, making a call to the appropriate 'Get' method with the UID value of the

 // required type

 exclusiveUse = extendedCryptoParams->GetTIntL(KExclusiveUseTypeUid);

 CleanupStack::PopAndDestroy(2, asymmetricCipherImpl);

 }

// Pop and destroy the remaining items on the cleanup stack

CleanupStack::PopAndDestroy(3,keyParams);

</codeblock>

</conbody></concept>